1. Field of the Invention
This invention relates to a solenoid valve in which a plunger is smoothly operated and which has a sufficient resistance against contamination of an operating oil.
2. Description of the Prior Art
In general, a solenoid valve has a plunger which is slidingly moved within a cylindrical body thereof by a magnetic force, and by the displacement of this plunger, the flow of a fluid may be regulated and other valves, may be switched over. When in use, these necessary operations are frequently performed. As a result, the plunger and the sliding surface of the cylindrical body are worn or damaged as time passes. As a result, the operation of the plunger becomes poor. Therefore, it is necessary to somehow prevent the plunger from becoming ineffective in operation.
In order to meet this requirement, there is known, for example, an operating oil introduction type solenoid valve, in which a cap containing a plunger therein is formed therein with an oil reservoir chamber communicating with the operating oil within an oil tank, and the oil reservoir chamber is communicated with a plunger chamber containing the plunger, thereby to feed the operating oil in the oil reservoir chamber to a space between the plunger and the inner peripheral surface of the cylindrical body for lubrication.
However, that solenoid valve has such a structure as to be dipped into the operating oil and used. Therefore, when, for example, the solenoid valve is taken out of the operating oil and used, the feeding of the operating oil to the oil reservoir chamber is cut. As a result, the lubrication of the plunger becomes poor and thus inconvenient.